You've correctly identified the key points for verifying compliance with 695.4(B)(2)(a)(2). Let's break down each requirement and how to approach verification

a. Not open within 2 minutes at 600% of FLC:
TCC Curve

This is the primary tool. You'll need the TCC curve for the specific overcurrent protective device (OCPD) being used (circuit breaker or fuse).

Procedure

1. Determine the full-load current (FLC) of the fire pump motor(s). This is usually found on the motor nameplate.
2. Calculate 600% of the FLC.3. Locate the 600% FLC value on the current axis of the TCC curve.
4. Draw a vertical line up from that point.5. The point where that vertical line intersects the OCPD's curve will tell you the clearing time at 600% FLC.
6. Verify that the clearing time is greater than 2 minutes.

b. Not open with a re-start transient of 24 times the full-load current of the fire pump motor(s)



The Time Component is Critical

You are right to question the timeframe for this transient. The NEC doesn't explicitly define it, but it's understood to be very short duration. We're talking milliseconds to fractions of a second. This is because the inrush current subsides quickly as the motor accelerates.

How to Approach Verification

This requirement is tricky and often involves relying on manufacturer data or testing, and is why OCPD's need to be listed for fire pump service.1.

Manufacturer's Data

The best approach is to request documentation from the OCPD manufacturer stating that their device is designed to withstand a 24x FLC inrush current for the expected duration of a motor start-up (e.g., milliseconds to a second). Look for phrases like "withstands motor starting currents" or "designed for high inrush applications." Fire pump-rated OCPDs are specifically designed to accommodate these starting surges.2.

TCC Curve (Limited Use)

You can look at the instantaneous trip region of the TCC curve. Ideally, you want the curve to show that the device can handle 24x FLC for a very short period. However, TCC curves often don't provide sufficient detail in the sub-second range for a precise determination.3.

Testing (Rare)

In extreme cases, you could theoretically perform testing by simulating a motor start-up with a controlled current source and monitoring the OCPD's behavior. This is complex and usually unnecessary if you have manufacturer documentation.

Why it's important

Fire pumps must start reliably. Nuisance tripping during startup is unacceptable. The OCPD needs to be able to distinguish between a brief inrush current and a sustained overcurrent condition.

c. Not open within 10 minutes at 300% of FLC



TCC Curve

Same procedure as with the 600% test, but now:1. Calculate 300% of the FLC.
2. Locate 300% FLC on the TCC curve.3. Draw a vertical line.
4. Verify that the clearing time at 300% FLC is greater than 10 minutes.

d. Trip Point Not Field Adjustable



Visual Inspection

This is usually straightforward. Look for any dials, switches, or other mechanisms on the OCPD that would allow for field adjustment of the trip current or time. Fire pump circuit breakers are usually sealed or have tamper-resistant covers to prevent unauthorized adjustments.

Important Considerations



Fire Pump Listing

The most important thing is to ensure the OCPD is listed specifically for fire pump service (UL 218). This listing means it has been tested and certified to meet the requirements of NEC 695. The manufacturer's listing information (e.g., UL listing mark) and documentation are crucial.

Coordination Study

A proper fire pump system design includes a coordination study. This study analyzes the characteristics of all overcurrent protective devices in the system to ensure selective coordination. The fire pump OCPD must be the last device to trip, allowing upstream devices to clear faults before interrupting power to the fire pump.

Documentation

Keep copies of the OCPD's listing information, TCC curves, and any manufacturer documentation that supports compliance with 695.4(B)(2)(a)(2).*

AHJ (Authority Having Jurisdiction)

The AHJ has the final say in determining compliance. Be prepared to provide them with the necessary documentation and answer their questions.In summary, focus on:1.

Using Fire Pump Listed OCPDs

This is the most reliable way to meet the requirements.2.

Obtaining Manufacturer's Data

Especially for the 24x FLC inrush.3.

Analyzing the TCC Curve

For the 600% and 300% FLC requirements.4.

Documenting Everything: For inspection and future reference.Remember that fire pump systems are critical life-safety systems. Thoroughness and careful attention to detail are essential. When in doubt, consult with a qualified electrical engineer experienced in fire pump system design. Flag for review